London: Software security experts have warned that cracking the TDL-4 botnet is not going to be easy, terming it as 'indestructible'.A botnet is a network of home computers that have been infected by a virus that allows a hi-tech criminal to use them remotely.
Botnet controllers often steal data from victims' PCs or use the machines to send out spam or carry out other attacks, reports the BBC News.
According to the experts, more than four million PCs have been enrolled in a botnet security. The botnet targets Windows PCs and is difficult to detect and shut down.
They further stated that the code that hijacks a PC hides in places that the security software rarely looks in and the botnet is controlled using custom-made encryption.
It is informed that nearly 4.5 million PCs have become victims over the last three months, following the appearance of the fourth version of the TDL virus.
Giving a detailed analysis of the virus, Kaspersky Labs security researchers Sergey Golovanov and Igor Soumenkov wrote that the changes introduced in TDL-4 made it the "most sophisticated threat today."
"The owners of TDL are essentially trying to create an 'indestructible' botnet that is protected against attacks, competitors, and anti-virus companies", the researchers added.
Statistically, the majority of victims, 28pc are in the US but significant numbers are in India (7pc) and the UK (5pc). However, in France, Germany and Canada, the numbers are smaller at 3pc.
The TDL virus spreads through booby-trapped websites and infects a machine by exploiting unpatched vulnerabilities.
According to experts, the virus has been found lurking on sites offering porn and pirated movies as well as those that let people store video and image files.